The name of the structure labeled as A is 'myosin'. Moreover, the name of the structure labeled as B is 'actin'.
A sarcomere is the basic unit of muscle contraction. This unit is defined as the region between two Z-lines.
Band A is a central band composed of the thick filaments of myosin.
Moreover, the sarcomere also has two halves of a band known as I-band, which consists of thin filaments of actin.
Muscle contraction is caused by the interaction between actin and myosin protein filaments in the sarcomeres.
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